Property, Plant, and Equipment
 9 Months Ended
Sep. 30, 2016
Property, Plant and Equipment [Abstract]  
Property, Plant, and Equipment
Property, Plant, and Equipment

The components of property, plant, and equipment were as follows (dollars in millions):
 
September 30,
2016
 
December 31,
2015
Land and land improvements
$
148.6

 
$
146.4

Buildings
687.8

 
640.9

Machinery and equipment
4,902.2

 
4,747.1

Construction in progress
151.2

 
119.1

Other
62.6

 
61.3

Property, plant, and equipment, at cost
5,952.4

 
5,714.8

Less accumulated depreciation
(3,073.7
)
 
(2,882.7
)
Property, plant, and equipment, net
$
2,878.7

 
$
2,832.1



Depreciation expense for the three months ended September 30, 2016 and 2015 was $79.9 million and $79.6 million, respectively. During the nine months ended September 30, 2016 and 2015, depreciation expense was $240.5 million and $243.5 million, respectively. During the nine months ended September 30, 2016 and 2015, we recognized $0.8 million and $9.0 million, respectively, of incremental depreciation expense from shortening the useful lives of assets related to facilities closures in 2016 and restructuring activities at our DeRidder, Louisiana mill in 2015.

At September 30, 2016 and December 31, 2015 purchases of property, plant, and equipment included in accounts payable were $20.1 million and $15.0 million, respectively.